Small amounts of fluoride in drinking water have been shown to improve oral health, according to Hope Saltmarsh, the oral health program director at the state Department of Health and Human Services.

The U.S. Centers for Disease Control and Prevention recently awarded six of New Hampshire’s 10 communities with water fluoridation programs its Water Quality Fluoridation Award. Water works departments in Manchester, Concord, Dover, Laconia, Lebanon and Lancaster were recognized for maintaining the target balance of fluoride levels through 2015.

“Fluoride is a very important aspect of keeping teeth healthy because it helps to make the enamel of the teeth stronger and more resistant to the decay process,” Saltmarsh said.

When the fluorides interact with our teeth, they act as microscopic masons, repairing tiny cracks and dents in the walls of our teeth, the enamel. That constant resurfacing and repair work (remineralization) slows down and guards against erosion (demineralization) from the acids we consume.

That’s no small thing for enamel.

“Natural enamel is very strong. It’s the strongest part of your body. It’s stronger than your bones,” Saltmarsh said.

The task for public water systems that fluoridate water is to strike the right balance. Fluoride is a natural substance already found in water, air and soil, so we are exposed to a certain amount of it already, and public health officials take that into account. Too little fluoride and our teeth’s repairmen will be understaffed; too much and it could lead to conditions like fluorosis, which only affects children (usually around 9 years old) whose teeth haven’t erupted yet and will make their teeth speckled from an uneven distribution of minerals on the enamel.

In 2015, national public health officials set .7 milligrams per liter as the optimal level for fluoride in drinking water. Prior to that, the standard was a range from .7 mgpl to 1.2 mgpl. Saltmarsh said the change was due to the growing number of other fluoride sources that people are exposed to.

While some conspiracy theorists believe water fluoridation is bad for various reasons, Saltmarsh said the science demonstrating its benefits is not in dispute. The CDC calls it the one of the top 10 public health achievements of the 20th century. And for every $1 of community investment in fluoridation, they save $38 in dental treatment costs.

Besides the six communities awarded by the CDC, public drinking water fluoridation programs are also in Durham, Rochester, Portsmouth and Hanover (while some neighboring communities might benefit as well), according to Saltmarsh.

With 47 percent of residents receiving fluoridated water, more than half — many of whom are on private wells — do not. That’s compared to 75 percent who receive fluoridated water nationwide.

The remaining majority of the state doesn’t necessarily need to worry about tooth decay, however. Some wells may already have a sufficient level of naturally occurring fluorides.

To be sure, residents can have their tap water tested at the State Lab. A standard analysis costs $85 and a fluoride-only test is $12. Call 271-3445 for more info about water testing.

If your water’s fluoride levels are low, you can get fluoride supplements, which are recommended for children when levels are .3 parts per million (roughly equivalent to milligrams per liter) or less.

The American Dental Association also recommends children brush twice a day with fluoridated toothpaste (about the size of a rice grain for kids 3 years old or younger) as soon as teeth begin to come in. Increase toothpaste to about the size of a pea for kids age 3 to 6.